Public Class Form1

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        With ListBox1.Items
            .Add("ani")
            .Add("bobi")
            .Add("dimo")
            .Add("ivan")
            .Add("mimi")
        End With
        With ListBox2.Items
            .Add("1111")
            .Add("2222")
            .Add("3333")
            .Add("4444")
            .Add("5555")
        End With
        'lstIme.Hide()
        'lstPas.Hide()
    End Sub

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim i As Integer
        Dim x As Integer
        Dim blnExists As Boolean

        If TextBox1.Text <> "" And blnExists = False Then
            TextBox1.Text = ""
            TextBox2.Text = ""
            MsgBox("НЕВАЛИДНО ПОТРЕБИТЕЛСКО ИМЕ", vbInformation, "Съобщение")
        End If


        For i = 0 To ListBox1.Items.Count() - 1
            For x = 0 To ListBox2.Items.Count() - 1
                If TextBox1.Text = ListBox1.Items(i) Then
                ElseIf TextBox2.Text = ListBox2.Items(x) Then
                    MsgBox("ПОЗДРАВИ за", vbExclamation, "СЪОБЩЕНИЕ")
                    Exit For
                Else
                    MsgBox("НЕВАЛИДНА ПАРОЛА", vbExclamation, "СЪОБЩЕНИЕ")
                    Exit For
                End If
            Next
        Next
    End Sub

    Private Sub CheckBox1_CheckedChanged(sender As System.Object, e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked = True Then
            TextBox2.PasswordChar = ""
        Else
            TextBox2.PasswordChar = "*"
        End If
    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        TextBox1.Clear()
        TextBox2.Clear()
    End Sub
End Class